The use of electric vehicles promises a solution to many problems presently associated with private transport: the power necessary to drive these can be created in an environmentally-friendly manner, no exhaust gases are produced by the actual vehicle, the noise level is reduced and the electric drive itself in principle allows a higher efficiency than an engine relying on the combustion of fossil fuels.
In order for electric vehicles to be more widely used, however, simple and geographically widespread opportunities must be provided for energy charging, similar to the familiar filling station network for liquid fuels. This also raises questions of deducting a payment and securing the charging process. At present, although an infrastructure for a power supply is at least geographically broadly in place, the energy consumption from a plug socket cannot be easily broken down by respective user and determined promptly, if necessary limited, and billed in situ.
In order to make power filling stations that can be used by anyone, that is to say publicly accessible charging stations, practical, these must be as easy to operate as petrol pumps for liquid fuels and also allow the similar possibility of limitation and billing for the charging. From the point of view of the vehicle user, therefore, as little as possible should change.
With known safety mechanisms that prevent the connector being pulled out, control of the mechanical interlocking takes place from the vehicle. The charging station also monitors if the connector has been plugged into the vehicle. When the connector is pulled out, the charging current is interrupted so that there is no danger from the charging connector as a result of the high electrical potential present on this.
However, this can also lead to a deliberate pulling out of the charging connector from the vehicle resulting in an interruption to the charging process. In particular in the event that the charging process has already been paid for prior to charging this should be avoided. In this case the user also wants the vehicle to charge at the charging station for the duration paid for. This is of particular relevance when charging with direct current. There is as yet no calibrated method with which during charging with direct current the quantity of energy obtained can be measured. Rather, when charging with direct current a charging time is measured. It must therefore be ensured that the charging time previously paid for is actually used to charge the vehicle.